Compositions which provide a combination of cleansing and conditioning to the hair are well know in the art. Such shampoo or shower-gel compositions typically comprise one or more surfactants for shampooing or cleansing purposes and one or more conditioning agents. The purpose of the conditioning agent is to make the hair easier to comb when wet and more manageable when dry, e.g. less static and fly-away. Typically, these conditioning agents are water-insoluble oily materials, cationic polymers or cationic surfactants.
Amongst the most popular conditioning agents used in shampoo products are oily materials such as mineral oils, naturally occurring oils such as triglycerides and silicone polymers. These are generally present in the shampoo as dispersed hydrophobic emulsion droplets. Conditioning is achieved by the oily material being deposited onto the hair resulting in the formation of a film.
Conditioning compositions which provide conditioning only, without cleansing surfactants, are also well known in the art. Such compositions are generally applied to the hair after the cleansing composition has been rinsed away.
Two methods are commonly used to enhance the deposition of conditioning oil droplets onto the hair.
One method is to use large droplets of oil, typically greater than 5 micrometers in diameter, typically with a viscosity in the range 5 to 500 Pa·s (measured at 25° C. and 21 s−). This method relies on physical contact between the hair and the droplets followed by the oil droplet wetting the hair surface and spreading.
Natural oils secreted by the sebaceous gland at the base of the hair lead to hair being more hydrophobic near the root rather than near the tip. This means that droplets deposited onto hair by the above methods are more likely to spread and form films on the hair at the base of the hair rather than near the tip of the hair, and this is found in practice.
Another method to enhance deposition of the conditioning oil droplets onto the hair, when the mean conditioning oil droplet size (D3,2) is less than 2 micrometers, is to employ a cationic deposition polymer in the composition. The use of such polymers is known in the prior art.
U.S. Pat. No. 3,753,916 discloses the use of cationic polymers as deposition aids.
The use of cationic polymers means that the oil droplets are flocculated with the cationic polymer on dilution of the shampoo when the hair is rinsed. This leads to indiscriminate deposition of the cationic polymer, conditioning oil and any other insoluble materials onto the hair. There is no specific targeting of the root or the tip regions of the hair. The presence of extraneous materials in addition to the conditioning oil can lead to dulling of the appearance of the hair (loss of shine) and also to a heavy feel to the hair (because of the presence of the cationic polymer).
Certain consumers find the effects arising from the two deposition methods described above to be undesirable in that they lead to the hair feeling greasy at the roots or heavy and dull.
In attempts to overcome these problems in the prior art, it has been considered desirable to target the deposition of the conditioning oil droplets onto the tip regions of the hair in preference to the root regions, and much research has been carried out in this field of work. Although it would be desirable to make the surface of the oil droplets more hydrophilic, it had always been considered that the high levels of surfactant in shampoo compositions would dominate the surface chemistry and hydrophilicity of the oil droplets. Thus the conventional view is that irrespective of additives added to the conditioning oil droplets, the shampoo surfactant would control the droplet hydrophilicity and deposition.
It has now surprisingly been found, that by combining certain types of surface active polymer with the small conditioning oil emulsion droplets in compositions also containing cationic deposition polymers, enhanced deposition of the droplets onto the tip regions of hairs can be achieved.
The surface active polymers required to provide this selective conditioning benefit are certain block copolymers of ethylene glycol and propylene glycol